Influence of Activators on Formation of Voids in Aluminum-Chromium Diffusion Coatings
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摘要: Ni襯底用粉末包裝法先擴散Al再擴散Cr時,在Al-Cr擴散層內產生了孔穴。它形成的原因是:活化劑NH4Cl加熱分解時生成HCl氣體,與已形成擴散層中的Al作用,使其從擴散層中逃逸,而在原來Al的位置上產生了孔穴。含有孔穴的Al-Cr擴散層的抗氧化能力明顯降低。Abstract: Aluminum-chromium diffusion coatings on pure nickel substrate were formed by two-step pack cementation process. It was found that existed many voids in the coatings which were formed by first aluminizing and then chromizing. It could be understood that aluminum in the coatings reacted with HCL gas decomposed from activator NH4CL and formed ACL3,which evaporated and resulted in formation of the voids.Oxidation resistance of Al-Cr coating with these voids was reduced signigicantly.
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Key words:
- halide activator /
- Al-Cr diffusion coatings /
- voids
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